Thirty years ago, personal computers did not exist, except in the dreams of a few people. And few noticed when two scientists started another electronics company in what became Silicon Valley.

Today, PCs are ubiquitous. And hardly anyone hasn't heard of Intel Corp.Intel, now the world's biggest maker of computer chips, helped change the world with devices the size of a thumbnail - the microprocessors that are the brains of most PCs.

"I may be a bit prejudiced, but I consider Intel's role to be very central. We got on the right horses . . . that to a very considerable extent have driven the entire computer revolution," said Gordon Moore, Intel co-founder and former chairman.

Moore, who remains on the company's executive committee, reflected on Intel's history, place in the industry - and the challenges it faces - as it quietly marks its founding 30 years ago this month.

Intel, after enjoying a record of nearly $7 billion in profits and $25 billion in revenues in 1997, is having a rough time in 1998. The company's earnings and sales have declined as demand has cooled. It faces significant competition in the fast-growing market for low-priced consumer PCs.

Intel frankly acknowledges those challenges, which is prompting it to reduce its work force 5 percent. It is vigorously pursuing the low end, expanding into server computers and exploring ways to enter the burgeoning market for the hand-held devices and Internet appliances that mimic some of the PC's functions.

Meanwhile, the company is continuing its strategy of producing increasingly powerful processors while cutting prices - and encouraging development of such features as video-conferencing that require its beefy chips.

"I think our challenge is to continue the growth of the market and the demand for high-performance computing," Moore said.

Industry observers debate how well Intel will be able to carry out that strategy. But no one expects the company to lose its dominant position any time in the foreseeable future. And no one denies Intel's contributions.

"Think about some of the great inventions that have really driven the world's economy. You have steam, you have electricity, you have the railroads," said Daniel Niles, an analyst with BankAmerica Robertson Stephens in San Francisco. "Semiconductors and PCs are the sort of thing that change the world and the way we work. And Intel is at the heart of that industry."

Intel was started on July 18, 1968, by Moore and Robert Noyce, an inventor of the integrated circuit. The two had been among the co-founders of Fairchild Semiconductor, a major producer of integrated circuits. They were soon joined by Andrew Grove, also a Fairchild employee.

The company began by making computer memory chips, supplanting the larger grids of small magnetic circles then used.

But the product that made Intel's fortune got its start in 1969, when the Japanese company Busicom asked it to make a set of custom chips for its new calculator. Intel engineers instead put 2,300 transistors on a single slice of silicon to create an all-purpose computer on a chip - the first microprocessor - which debuted in 1971.

The first microprocessors ended up in traffic lights, cash registers, gas pumps and other devices. But in 1974, an Intel microprocessor was used in the Altair, the world's first personal computer, which was sold in kits.

The big break came in 1980, when IBM chose Intel's 8088 chip over competitors' processors for its line of personal computers. In the mid-1980s, Intel switched its focus from memory chips to processors - then prospered as IBM-type computers with its chips and Microsoft Corp.'s operating software became the de facto industry standards. Intel's chips are now the "brains" of more than 80 percent of all PCs.

Intel has been admired for its management and its ability to turn out huge volumes of complex chip. But part of its success, Moore said, was luck.

"We were fortunate to be in the right place at the right time and made some good decisions," he said.

Moore served as Intel's chairman until mid-1997, when he was succeeded by Grove, then chief executive officer. Grove gave up the CEO role earlier this year to president Craig Barrett. Noyce, who had been chairman then vice chairman, died in 1990.

Now 69, Moore may be best known for "Moore's Law," his accurate prediction - made in 1965 - that manufacturers would be able to regularly double the number of transistors on a chip and the chip would remain the same price.

Making ever-more-powerful processors is how Intel has thrived. The 8088 chip ran at 8 megahertz and had 29,000 transistors; the current flagship Pentium II runs at 400 Mhz and boasts 7.5 million transistors.

Computer users, however, don't need that kind of power if all they're going to do is balance checkbooks, send electronic mail and surf the Internet, Moore concedes. But the company is betting that businesses and many consumers many will find powerful PCs necessary if they want to make video phone calls, have their machines understand voice commands, play sophisticated games - or do some tasks that haven't even been imagined yet.

After all, who 30 years ago thought individuals could ever afford computers? Who imagined they could do what they do now?